Were monster munch crisps a lot bigger than they are today??

I think this is true of most things.
Remember when Wagon Wheels where just that and it was really difficult to get a whole one in your mouth.

For the Yanks here's what we are talking about:

http://img222.imageshack.us/img222/9776/walkersmm14bp8.jpg
http://www.britsuperstore.com/acatalog/Burtons_Original_Wagon_Wheels_8_Pack.jpg

I tend to think that also - candy bars sure seem to be smaller and not as good as they were. Bags of the yummy (not healthy) snacks are smaller and more expensive. Used to be a strawberry pop tasted like a strawberry and not chemicals. Progress...